Relation between knee extensors' strength, postural stability and variability of centre of pressure displacement during gait in adult women

Objective: The aim of this study was to investigate the relation between knee extensors' strength, centre of pressure (COP) velocity during one-leg stance and variability of COP displacement during various phases of gait cycle in middle-age women.

Methods: A single group of 40 healthy women (age 56 ± 4.2 years) took part in the study. For assessment of knee extensors' strength (peak torque and average work during concentric and eccentric contractions) an isokinetic dynamometer was used. Mean velocity of COP during one-leg stance in anterior-posterior (AP) and medial-lateral (ML) directions was assessed on a force plate on a rigid surface with eyes open (two 30 s trials). Variability of COP displacement was assessed for loading response, midstance, terminal stance and preswing gait cycle phases (determined by vertical ground reaction force) in AP and ML directions. It was measured by two force plates positioned in the middle of an 8 m walkway (5 trials at a self-selected speed). For statistical analysis of relationships between variables Pearson correlation was applied.

Results: Our results showed significant correlations between eccentric peak torque and COP velocity in AP direction during one-leg stance, eccentric and concentric peak torque and COP variability during loading response in both ML and AP directions and during terminal stance in AP direction.

Conclusion: Loading response and terminal stance seems to be more related to knee extensors' strength. Variables derived from postural stability assessment during one-leg stance are independent from variables derived from assessment of COP displacement variability during walking.